Tracking-system



Feb. 21, 1956- C. E. VOGELEY, JR., ET AL PHASE-COMPARATOR TRACKING-SYSTEM Filed Nov. 2, 1948 Fig. 2M1.

IAMPLIFJER IAZ r I I I I l I I l I I T/\ I I 30: I AMPLIFIER I-A 1 I I I I I I I I0 fix/27E?" 6'! L] I n 3.

INVENTORS Clyde 6'. V'oyeleyJliana Tfzeadore Mzllerl ATTORNEY United States PHASE-CQMPARATOR TRACKING-SYSTEM Application November 2, 1948, Seriai No. 57,936 11 Claims. (Cl. 343-7.4)

Our invention relates to a novel type of automatic radar tracking-system or the like, and to a novel type of phasecomparator which is particularly adapted for our automatic radar tracking-system, but which is susceptible of other uses, separate from the tracking-system. Our invention is particularly adapted for continuous-wave radar, although it can be used in connection with any kind of transmitter-system or systems which send out either high-frequency radio-waves, or radar-waves (or micro-waves), or lower-frequency waves (such as supersonic or sonic waves), which are reflected back to our target-tracking echo-wave device; or our target-tracking device may be used to track a target which is transmitting radiation or wave-energy of a given frequency, as distinguished from merely reflecting a radiation or waveenergy with which it is illuminated.

object i our invention is to provide a target-tracking wave-device comprising a directional receiving-antenna system which includes two spaced, substantially parallel-aimed antenna-means, for receiving two waves of the same frequency from the target, in combination with a suitable phase=comparator which will very sensitively show which of the two incoming waves is lagging, in phase, behind the other.

A further object of our invention is to provide a novel type of phase-comparator means, which is particularly adapted for use in our target-tracking means, but which is susceptible of other phase-comparator uses.

More specifically, it is an object of our invention to provide a phase-comparator for responding to the relative phase-angle between .two input-waves, comprising means for providing two resultant-waves, which are provided by vectorially combining the two input-waves, after having introduced a certain leading-angle, in one of the input-waves, in order to obtain the first resultant wave, and after having introduced a certain lagging angle, in the same input-wave, in order to obtain the second resultant-wave, in combination with means for comparing the relative magnitudes of the two resultant-waves.

With the foregoing and other objects in view, our invention consists in the systems, circuits, parts, and methods of design and use, hereinafter described and claimed, and illustrated in the accompanying drawing, wherein:

Fig. 1 is a block-diagram illustrating, with considerable simplification, the essential component-parts and connections of an illustrative form of embodiment of our invention;

Figs. 2a, 2b, and 2c are vector-diagrams which will be e e r d to in th explanation of-the invention, d

Fig. 3 is a fragmentary view illustrating a modification of apart of Fig. 1.

In Fig. 1, we have illustrated a simple form of our invention which is used only in azimuth-tracking of a ate t 2,736,019 Patented Feb. 21, 1956 target. This illustrates the general principles of the target-tracking phase of our invention, because when elevation-tracking is necessary, the elevation-tracking apparatus is merely a repetition of the azimuth-tracking apparatus, turned at right angles.

In the illustrative form of embodiment of our invention, as shown in Fig. 1, a radiant-energy transmittersystem is diagrammatically indicated, as comprising a transmitter 5, operating at x megacycles (mo). This transmitter is preferably a continuous-wave transmitter, although our invention is not limited to this particular type of transmitter, 1

This transmitter 5 is used as a part of a target-tracking echo-wave device, which includes a directional antennasystem for aiming a transmitted wave from said transrnitter to a target (not shown) and for receiving an echowave from the target. This directional antenna-system may take any one of a number of forms, which are well known in the art; and it may comprise either one antenna or a plurality of separate, mechanically connected an tennas. By way of illustration of a representative type of antenna-system, without in any way desiring to limit ourselves to this particular type of antenna-system, we have shown a directional antenna-system comprising three horns, a horn H for transmitting the wave from the transmitter 5, and two horns H1 and H2 for receiving two echowaves A and B from the target, these receiver-horns H1 and H2 being spaced by a distance ab, and being directed in lines parallel to each other, and hence, in parallel to the antenna-aiming direction MM, which may be regarded as a line drawn half-way between the two receiving-horns H1 and H2.

The two receiver-horns H1 and H2 feed the respective received waves A and B into suitable input-circuit wave-conducting means, such as waveguides 11 and 12, which feed the respective input-waves A and B into two spaced orifices 0-1 and 0-2 in a main waveguide 13. The main waveguide 13 is intended to be representative of any transmission-line means for transmitting electromagnetic wave-energy, and the orifices 0-1 and 0-2 are intended to be representative of any tapped points, of such nature that, at each tapped point, the input-wave is split into two parts which travel in opposite directions along the main waveguide or transmission-dine 13. Thus, the input-wave A is divided into two waves, k1A and kzA, traveling respectively to the left and to the right, along the main waveguide 13, from the orifice 0-1. In like manner, the input-wave B is split into two parts, ksB and k4B, traveling respectively to the left and to the right along the main waveguide 13, as indicated in Fig, 1.

Within certain limits, the several coefficients k1 t0 k4.

may have any relative values, according to the design of the main transmission line 13.

In the main waveguide 13, the two orifices O-1 and 2 are at spaced immediate points between two crystals C1 and C2, or other detector-means for responding to the resultants R1 and R2 of the waves, which appear at these crystals. Thus, at the left-hand crystal C1, the two waves krA and ksB combined vectorially to produce the resultant-wave R1; whereas, at the right-hand crystal C2, the two waves kzA and k4B combine vectorially to produce the resultant-wave R2.

Any suitable means are provided, for suitably responding to, and rectifying, the two resultant-waves R1 and R2, and for comparing the relative magnitudes of the rectified waves, so as to determine whether the ratio of the magnitudes of the resultant-Waves, R1/R2 is increasing or decreasing above or below a predetermined norm. An illustration apparatus is indicated by block-diagram in Fig. 1, in which the incoming signals are rectified at the crystals C1 and C2, fed at R1 and R2 to direct-current amplifiers A1 and A2, respectively, and then are fed, through the amplifier output-leads L1 and L2, to the terminals of two bridge-resistors RA and RB, respectively.

The two resistors RA and RB constitute two of the arms of a bridge 23, which is composed of these two resistors RA and RB, and to two other resistors R1 and R2, the latter two resistors being indicated as being variable. One of the bridge-diagonals, such as the diagonal between the bridge-points 24 and 25, is supplied with a unidirectionalcurrent voltage from a suitable source such as battery 26 in series with a variable resistor R3. The other bridgediagonal, comprising the bridge-points 27 and 28, is connected to a control-circuit L3 which is used to control an automatic azimuth-control apparatus 29, which is mechanically connected to the antenna-system H1 and H2, as diagrammatically indicated by dotted lines at 30.

In the operation of the target-tracking part of our invention, the first essential is that, if the directed antennasystem is exactly on line with the target, the two received waves A and B reach the horn-centers a and b exactly in phase with each other, whereas, if the directed antennasystem is off-center with respect to the target, as shown in Fig. 1, the two received waves A and B reach the horncenters a and b considerably out of phase with each other, so that this circumstance can be responded to by suitable phase-comparator means.

1 In Fig. 1, let us assume that the spacing between the received-wave horn-centers a and b of the antenna-system is ab=SA where is the wavelength of the reflected wave which comes in through the air (or other medium) from the target (not shown).

' Let us assume that the target is displaced from the antenna-pointing direction MM, (which is normal to ab), by a target-angle 0, counting this target-angle as being positive if the target is to be right of the antenna-pointing direction MM, as shown in Fig. 1, and counting this target-angle 0 as being negative if the target is to the left of the antenna-pointing direction.

' The distance to the target (not shown) will be very large as compared to the antenna-spacing ab=SA)\, and hence we may consider that the two received waves A and B come in, to the horns H1 and H2, respectively, on parallel lines a'a and bb, respectively.

If we drop a perpendicular be onto the line aa, it will be obvious that the two waves A and B, on arriving at the points 0 and b, respectively, will have traveled equal distances from the target, and hence will be in phase with each other at these points.

' Before reaching its receiver-horn, the first received wave, A, will have to travel further than the second received wave, B, by the length of the line ca, which we may express, in terms of the wavelength x, as being ca=P)\.

From the triangle acb it is evident that P=SA sin 0 at all values of the target-angle 0 and when 0 is in degrees and is small.

The wave A, of wavelength A, in traveling a distance ca=P t, will become more lagging in phase by a phaseangle 0=360 P=6.28 SA0=27TSA6D (3) when 0 is small, and

0:360 P=360 SA sin 0 (4) when 0 is large.

It will be seen, from Equation 3, that if the target becomes displaced from the antenna-pointing direction by only as mall angle 0, we will obtain a large phase-angle difference, between the two incoming waves A and B, at the horn-centers a and b, respectively, said phase-difference being 27ISA times the target-displacement-angle 0 in the plane of the paper in Fig. 1, where SA is the number of wavelengths A in the antenna-spacing ab=SA7\. It is obvious that the multiplication of the sensitivity of response to the target-angle 0 is increased, the larger we can make the antenna-spacing ab=S4L However, the more we increase SA, the narrower will be the range of target-angles 0 over which our apparatus will be able to hold onto the target, or properly respond to its angle 0. A practical limit of proper responsiveness is reached when the double phase-displacement angle, 2 (responding to the two sides of the antenna-pointing direction), becomes or, if symmetry of response is obtained whether the target-angle 0 is positive or negative, 3. practical limit is reached when P becomes as large as A in Equation 4. Putting P A in Equation 1, we see that the range of target-angle 0 to which our apparatus is properly responsive, without requiring correction, is given by the inequality,

After the incoming waves A and B reach the horncenters :1 and b, the waves travel through waveguides, and we are interested in the guide-wavelength )t If the waves A and B traverse guide-lengths HA7\g and Hnk respectively, in reaching the orifices O1 and 0-2, respectively, and if these orifices 0-1 and O-2 are spaced by Swx and if the orifice O-l is spaced from the crystals C1 and C2 by TAg and Uk respectively, we can calculate the phase-differences 51 and z which are obtained between the two waves which reach each of the respective crystals C1 and C2, as follows.

At the left-hand crystal C1, the wave kaB will have traveled further than, (and hence will lag behind), the wave klA, by the distance At the right-hand crystal C2, the wave kzA will have traveled further than, (and hence will lag behind), the wave k413, by the distance,

At the respective crystals C1 and C2, the phase-difference-angles, G1 and 62, due to the traversal of the waveguide by the waves, are equal to 360 times the fractional or decimal parts of the numbers and (SW+HAHB), respectively.

At both of the crystals C1 and C2, we obtain the same phase-difierence-angle, =21rSA, due to the traversal of the distance ca=P)t in air, as expressed in Equation 3, this phase-angle being subtracted from G1 at the crystal C1, and being added to 62 at the crystal C2, as shown in Equations 6 and 7.

The phase-difference between the two incident waves ksB and kiA at the left-hand crystal C1 is therefore 1=G1-=G1-21rSA6 (8) The phase-diiference between the two incidentwaves KzA and k4B at the right-hand crystal C2 is I 2=G2+=G2+27TSA60 (9) The magnitude of the total or resultant-wave R1- at the left-hand crystal C1 is shown by the equation,

R1 =k1 A1 +k3 B +2k1k3AB cos l=kl A k3 B +k1k3AB (cos G1 cos +sin G1 sin (10) The magnitude of the total or resultant-wave R2 at the right-hand crystal C2 is shown by the equation,

sateen Our invention operates on the principle of comparing the relative magnitudes of the two resultant-waves R1 and R2, and hence it is desirable for the constant or non-directional angle-components G1" and G2 to be as close to either plus or minus 90' as possible, at which values the cosines .of the resultant angles 1 and 2 of Equations 8 and 9 will be varying at their maximum rate in response to Variations in said resultant-angles 1111 and 52. In this way, the variable or target-directional angle-components which are dependent upon the olf-center angle 0 of the target, will produce a maximum change in the values of the respective resultant waves R1 and R2. At any rate, the waveguide-produced constant angles G1 and G2 must not be equal to either zero or 180", because I then the resultant-Waves R1 and R2 would be equal in magnitude, whatever might be the value of the oft-center target-angle 6.

It is convenient to design the waveguide so that the horn-to-orifice distances Hin and Hnh are either equal or difierent from each other by a whole number of guidewavelengths A so that the constant guide-produced angle-components G1 and G2 will be equal to 360 times thedecimal or fractional part of the coefficient Sw which defines the orifice-spacing SW)\g in the wave guide. Hence SWhg must be equal to an odd number of quarter-Wavelengths A /A of the Waves in the waveguide, for optimum conditions (thus giving an angle equal to 90 or 270*), and can not under any circumstances be equal to an even number of quarter-wavelengths 7lg/4 (which would give an angle of zero or If 1 the guide-produced angle-components G1 and G2 are equal to +90", for example, Equation 10 and '11 become and R2 =k2 A l-k4 B -2k2k4/1B sin & (11') where the directionally responsive angle-component, ago is as defined in Equations 3 and 4, being rapidly variable in response to small changes in the target-dimotion 0 with respect to the centerline MM of the antonna- Figs. 2a, 2b and 2c show the vector-diagrams for the two resultant-waves R1 and R2, according to Equations 10' and ll, under conditions when (a) the target is o l-center, or his zero; (b) the target is to the right of the aniennarpointing direction MM, as shown in Fig. 1, or 0 is positive; and (c) the targetis cit-center to the lef r 0 is ega e It will be n te ha th ratio .Ri/Rz of e ma n f t wo r u t nt- Waves R1 nd R2 b com arger w n he t r -an le i p s i e o he right), a s m s ler when the target-angle g9 is negative (or to the left).

The bridge 23 is b o i t b n e as by djus ment of one or both of the variable resistors R1 R2, at any desired value of the ratio 121/122 of the two resultant-Waves R1 and h, as, (for example), under the conditions when the directional antennae system is exact- 1y on-target, Under these conditions, since the bridge is balanced, the output-voltage of the bridge is zero, in the output=circuit L3 of the bridge.- Then, if the target moves very slightly to the right, as viewed in Fig. s tha t t rg tg e 0 is P s t he firs resul antwave R1 becomes larger, as shown in Equation 10. or l0 and in Fig. 21;, while the second resultant-wave R2 becomes sm ler. as sho n by Eq ation 1 or .1, and as also shown in Fig. 2b, as will be seen in comparing 6 Fig-21 ith i 0h the other hshd, if t e tar et should move ofi-center to the left, so that the angle? becomes negative, it will be the second input-wattle 1; which lags behind the first inputawave A, as it reaches the a m em, so th t t e firs r sult nt-wave R; becomes smaller, and the second resultant-wave R; becomes larger, as shown in Fig. 2c, as also Will be seen o h equations, i a minus al i a signed o the phase-angle 0.

The bridge 23 will be thrown off-balance by these changes in the relative magnitudes of th rehullantwayes 1 and R2 so ha th bri g p oduces an ou p voltage which varies in sign and magnitude in accordance with the relative magnitudes of the two resultant- Waves R1 and R2, thereby producing a variable unidirectional voltage of one polarity or the other, which can be used for automatic-tracking purposes, that is, to re: aim the antenna-system so that it keeps exactly on-targ t, di gr m tic l y indi at d Fi will be u er t d that the br dg 2 i mere y cxemplification of suitable apparatus for resp ng to h g i the ratio Ii /R2 o the a p itudes o hi snitudes of the two resultant-waves R1 and V It will also be observed that our system is selfebal: ancing, so that the correcting signals which a tained in the output-circuit L3 .of the bridge ar indie..- pendent of the range of the target or the echo-area of the target.

Furthermore, while we have described our system more p t ly W I p t to azimu hont ol it be obvious that a duplicate of the same system, turned at right angles, could also bs used to obtain correctionsin va is ould imply a ra gem nt f a hirestional receiver antenna system which is operative in eleva= tion as well as in azimuth. if the receiver-antenna system is n t e o m of rns carry ut ou orig n lust a tion), this would imply fourhorns, these horns including the two previously described azimuth-finding horns H1 and H d wo he l a ion-fihs h h rns (not shown).-

1 .n a to th ph se-compa t pa t of our n en-- t on, i w l e se ed ha hi e W h i ust ated ou P a e-compara o as be mpo ed of wav uides, it is generally applicable to any wave conductingineans or transmission-line in which the conducted or transmitted wave sufiers a phase-shift as it travels along the phase, conductor or guide or line.

An es nti di t nct ve ovel t r f ur ew m tho nd m n f p s o ps i h s isc rni e i om Equa s v6 i, em mb r ng that a a eguidedie those which is e pre sed n rms o a o fiisi ht times the guiderwavelength A represents a phase angle lag hi is q a o 0 times t e cim or ra ional part of said coefiicient. in Equations 6 and 7 the coe i n P pr n s he Ph -s of 4 in he fir t r eived Wave A h s s epe n pon th t rg t: angle 0, as shown in Equation 3.

Referring to the parts of Equations 6 and 7 which relate to the phasershifts which are introduced in the W u d phas mp t hat is, re er ng o the de ma P rt o he oef i i n s of the guideavelength A it will be noted that the left-hand derived-wave ksB of the, second input-wave B is in efiect lagged in phase by a x d c mp n nt, s p ese t d by he dec m p t of t ooo i i t Sw m e than t a unt by h ch he l f -h n d ri ed a kiA o th first flP l'W P A is a ge n th a e d p asempar to w er as n e s o th or h -h nd e i d ves MB nd zA, h fii e w s a e tive sign, ndica ing t at this is a leading phase-shift, rather than, a laggin P1 5? hiflo he rds, an e en i l fu men al tea im oi our new phase-comparator is that each oi the two in.- Puh s .A and -shall b use t b in tw d r W hssho n a l n to the igh a left r sp cti ly, and the two lettehand derived waves are vectoriallywmbined to produce a first resultant-wave R1, while the two right-hand derived waves are vectorially combined to produce a second resultant wave R2, but only after the phase-comparator apparatus has introduced a phase-shift angle which lags more, in the left-hand component of the second input-wave B, than in the left-hand component of the first input wave A, whereas the waveguide phasecomparator as introduced a phase-shift angle which lags less, in the right-hand derived wave of the second inputwave B, than in the right-hand derived wave of the first input-wave A.

"These leading and lagging phase-angles which are introduced in the waveguide approximate an optimum value of an odd multiple of 90, corresponding to an orificeseparation of an odd number of quarter-wavelengths along the guide. These angles, at any rate, can not be equal, or nearly equal, to zero, or any multiple of 180. corresponding to an orifice-separation of zero or a multiple of a half-wavelength or an even multiple of a quarterivavelength. The two resultant-waves need only to be compared in magnitude, to obtain a response to the phaseshift angle which is responsive to the target-angle 9, as previously pointed out.

' As an example of one of the many changes in detail, which may be incorporated in our invention, we have shown, in Fig. 3, a modification of Fig. 1, in which the input-circuit waveguides 11 and 12 are provided with crystal modulators CM1 and CM2, respectively, which amplitude-modulate the two input-waves or signals A and B at megacycles, as supplied from a local oscillator 31. Here, the frequency of 10 megacycles is given only by way of example, as any suitable modulating frequency might have been chosen. In Fig. 3, the amplification of the resultant-waves R1 and R2 is made at the modulatorfrequency, as indicated by the IO-megacycle amplifiers 41 and 42, which are substituted for the input-wavefrequency amplifiers A1 and A2 in Fig. l. The outputs of the ltl-megacycle amplifiers 41 and 42 are then fed, through circuits 21 and 22, to 10 megacycle-detectors or rectifiers, 51 and 52, respectively, the output-circuits of which are equivalent to the output-circuits L1 and L2 of Fig. 1, which constitute the control-circuits for the bridge. The changes which are introduced in Fig. 3 make the system more sensitive, and enhance the signal-to-noise ratio, as will be readily understood.

While we have particularly described and claimed two exemplary-forms of embodiment of our invention, and while we have explained our present ideas relative to its design and performance, we do not wish to be limited to the precise illustrations and explanations which we have given, as it will be obvious that various changes may be made by the skilled workers of the art, by way of additions orrefinements, omissions or simplifications, or the substitution of various equivalents, without departing from the essential features of our invention, in its various aspects.- We desire, therefore, that the appended claims shall'be accorded the broadest construction consistent with their language.

We claim as our invention:

1. A target-tracking echo-wave device, comprising a transmitter-system, a directional antenna-system for aiming a transmitted wave from said transmitter-system to a target and for receiving an echo-wave from said target, at least the receiving part of said directional antennasystem including two spaced, substantially parallel-aimed antenna-means for in eflect receiving two echo-waves A and B from said target, a phase-comparator for responding to the relative phase-angle between the two-inputwaves A and B, said phase-comparator comprising means for obtaining, from Wave-A, two derived A-waves having certain phase-shifts introduced therein, means for obtaining, from wave-B, two derived B-waves having certain phase-shifts introduced therein, the phase-shift introduced in the first derived B-wave being greater than the phase-shift introduced in the first derived A-wave by a certain angle, and the phase-shift introduced in the '8 second derived B-wave being less than the phase-shift introduced in the second derived A-wave by a certain angle, said certain angles approximating an optimum value equal to an odd number of means for vectorially combining the first derived A-wave and the first derived B-wave to produce a first resultant-wave, means for vectorially combining the second derived A-wave and the second derived B-wave to produce a second resultantwave, means for comparing the relative magnitudes of the two resultant-waves, and automatic antenna-aiming means for correcting the antenna-aim in one direction or the other, according as the ratio of the magnitudes of the two resultant-waves increases or decreases above or below a value corresponding to on-target conditions.

2. A target-tracking echo-wave device, comprising a transmitter-system, a directional antenna-system for aiming a transmitted wave from said transmitter-system to a target and for receiving an echo-wave from said target, at least the receiving part of said directional antennasystem including two spaced, substantially parallelaimed antenna-means for in effect receiving two echowaves A and B from said target, a phase-comparator for responding to the relative phase-angle between the two input-waves A and B, said phase-comparator comprising means for obtaining, from wave-A, two derived A-waves having certain phase-shifts introduced therein, means for obtaining, from wave-B, two derived B-waves having certain phase-shifts introduced therein, the phaseshift introduced in the first derived B-wave being greater than the phase-shift introduced in the first derived A-wave by a certain angle, and the phase-shift introduced in the second derived B-wave being less than the phase-shift introduced in the second derived A-wave by a certain angle, said certain angles being substantially difierent from zero or any multiple of means for vectorially combining the first derived A-wave and the first derived B-wave to produce a first resultant-wave, means for vectorially combining the second derived A-wave and the second derived B-wave to produce a second resultantwave, means for comparing the relative magnitudes of the two resultant waves, and automatic antenna-aiming means for correcting the antenna-aim in one direction or the other, according as the ratio of the magnitudes of the two resultant-waves increases or decreases above or below a value corresponding to on-target condition.

3. A target-tracking wave-device, comprising a directional antenna-system including two spaced, substantially parallel-aimed antenna-means for in effect receiving two waves A and B of the same frequency from said target, a phase-comparator for responding to the relative phaseangle between the two input-waves A and B, said phasecomparator comprising means for obtaining, from wave-A, two derived A-waves having certain phase-shifts introduced therein, means for obtaining, from wave-B, two derived B-waves having certain phase-shifts intro duced therein, the phase-shift introduced in the first derived B-wave being greater than the phase-shift introduced in the first derived A-wave by a certain angle, and the phase-shift introduced in the second derived B-wave being less than the phase-shift introduced in the second derived A-wave by a certain angle, said certain angles approximating an optimum value equal to an odd number of 90, means for vectorially combining the first derived A-wave and the first derived B-wave to produce a first resultant-wave, means for vectorially combining the second derived A-wave and the derived second B-wave to produce a second resultant-wave, means for comparing the relative magnitudes of the two resultant-waves, and automatic antenna-aiming means for correcting the antenna-aim in one direction or the other, according as the ratio of the magnitudes of the two resultant-waves increases or decreases above or below a value corresponding to on-target conditions.

4. A target-tracking wave-device, comprising a directional antenna-system including two spaced, substantially arsenic 9 parallel-aimed antenna-means for in effeot receiving two waves A and B of the samefrequency from said target, a phase-comparator for responding to the relative phaseangle between the two input-waves A and B, said phasecomparator comprising means for obtaining, from wave-A, two derived A-waves having certain phase-shifts introduced therein, means for obtaining, from wave-B, two derived B-waves having certain phase-shifts introduced therein, the phase-shift introduced in the first derived B-wave being greater than the phase-shift introduced in the first derived A-Wave by a certain angle, and the phase-shift introduced in the second derived B-wave being less than the phase-shift introduced in the second derived A-wave by a certain angle, said certain angles, being substantially different from zero or any multiple of 180, means for vectorially combining the first derived A-wave and the first derived B-wave to produce a first resultant-wave, means for vectorially combining the second derived A-wave and the second derived B-wave to produce a second resultant-wave, means for comparing the relative magnitudes of the two resultant waves, and automatic antenna-aiming means for correcting the antenna-aim in one direction or the other, according as the ratio of the magnitudes of the two resultant-waves increases or decreases above or below a value corresponding to on-target conditions.

5. A phase-comparator for responding to the relative phase-angle between two input-waves A and B, said phasecomparator comprising means for obtaining, from wave- A, two derived A-waves having certain phase-shifts introduced therein, means for obtaining, from wave-B, two derived B-waves having a certain phase-shifts introduced therein, the phase-shift introduced in the first derived B-wave being greater than the phase-shift introduced in the first derived A-wave by a certain angle, and the phase-shift introduced in the second derived B-wave being less than the phase-shift introduced in the second derived A-wave by a certain angle, said certain angles approximating an optimum value equal to an odd number of 90, means for vectorially combining the first derived A-wave and the first derived B-wave to produce a first resultantwave, means for vectorially combining the second derived A-wave and the second derived B-wave to produce a second resultant-wave, and means for comparing the relative magnitudes of the two resultant-waves.

6. A target-tracking echo-wave device, comprising a transmitter-system, a directional antenna-system for aim! ing a transmitted wave from said transmitter-system to a target and for receiving an echo-wave from said target, at least the receiving part of said directional antennasystem including two spaced, substantially parallel-aimed antenna-means for in efiect receiving two echo-waves from said target, a main waveconducting means having two spaced detector-means and twointermediate tapped points between said detector-means, two input-circuit wave-conducting means for feeding wave-energy into the two tapped points, from the two antenna-means, respectively, in such manner that the input wave-energy which comes into the main wave-conducting means at each of said tapped points divides and travels as two waves to the respective detector-means, means for taking 01f a resultant-wave from each of said detector-means, means for separately responding to, and rectifying, the two resultantwaves, and comparing the same with each other in such a way as to obtain, in eifect, a unidirectional controlvoltage which varies in sign and magnitude in accordance with which one of the two resultant waves is the stronger, and automatic antenna-aiming means, responsive to said control-voltage, for so controlling said antenna-system as to track the target in the plane of said two spaced antenna-means.

7. An echo-wave device, comprising a-transmitter-systern, a directional antenna-system for aiming a transmitted wave from said transmitter-system to a target and for receiving aneclio wavirom said target, at least the re ceiving part of said directional antenna-system including two p ced subst nt ally par lel-aimed. ante n for in eflect receiving two echo-Waves from said target, a main wave-conducting means having two spaced detector-means andtwo intermediate tapped points between said detector-means, two input-circuit wave-conducting means for feeding wave-energy into the two tapped points, from the two antenna-means, respectively, in such manner that the input wave-energy which comes into the main wave-conducting means at each of said tapped points divides and travels-as two waves to the respective'detectormeans, means for taking ofl? a resultant-wave from eaeh of said detector-means, and means for separately responding to, and rectifying the two resultant-waves, and comparing the same with each other in such a way as to obtain, in eiTect, a unidirectional control-voltage which varies in sign and magnitude in accordance with which one of the two resultant-waves is the stronger.

8. A target-tracking wave-device, comprising a directional antenna-system including two spaced, substantially parallel-aimed antenna means for in eifect receiving two waves of the same frequency from said target, a main wave-conducting means having two spaced detector-means and two intermediate tapped points between said detectormeans, two input-circuit wave-conducting means for feeding wave-energy into the two tapped points, from the two antenna-means, respectively, in such manner that the input wave-energy which comes into the main Wave-conducting means at each of said tapped points divides and travels as two waves to the respective detector-means, means for taking off a resultant-wave from each of said detector-means, means for separately responding to, and rectifying, the two resultant-Waves, and comparing the same with each other in such a way as to obtain, in effect, a unidirectional control-voltage which varies in sign and magnitude in accordance with which one of the two re sultant waves is the stronger, and automatic antennaaiming means, responsive to said control-voltage, for so controlling said antenna-system as to track the target in the plane of said two spaced antenna-means.

9. A wave-device, comprising a directional antennasystem including two spaced, substantially parallel-aimed antenna-means for in efiect receiving two waves of the same frequency, a main wave-conducting means having two spaced detector-means and two intermediate tapped points between said detector-means, two input-circuit wave-conducting means for feeding wave-energy into the two tapped points, from the two antenna-means, respectively, in such manner that the input wave-energy which comes into the main wave-conducting means at each of said tapped points divides and travels as two waves to the respective detector-means, means for taking off a resultant-wave from each of said detector-means, and means for separately responding to, and rectifying, the two resultant-waves, and comparing the same with each other in such a way as to obtain, in effect, a unidirectional control-voltage which varies in sign and magnitude in accordance with which one of the two resultant waves is the stronger.

10. A wave-device, comprising a directional antennasystem including two spaced, substantially parallel-aimed antenna-means for in effect receiving two waves of the same frequency, a main wave-conducting means having two spaced detector-means and two intermediate tapped points between said detector-means, two input-circuit waveconducting means for feeding wave-energy into the two tapped points, from the two antenna-means, respectively, in such manner that the input Wave-energy which comes into the main wave-conducting means at each of said tapped points divides and travels as two waves to the respective detector-means, and means for taking oif a resultant-wave from each of said detector-means.

11. The wave-device as defined in claim 2 with the two References Cited in the file of this patent UNITED STATES PATENTS Reich Aug. 27, 1935 Guanella July 25, 1939 Goldstein Dec. 22, 1942 Donaldson Oct. 1, 1946 Hansen Dec. 3, 1946 Woodyard Dec. 3, 1946 Chubb Feb. 18, 1947 Korman July 1, 1947 Shepherd Aug. 5, 1947 12 Stearns Sept. 9, 1947 Hebb Jan. 6, 1948 Evans July 13, 1948 Agate et a1. Dec. 21, 1948 Blewett Apr. 12, 1949 Ridenour June 14, 1949 Barrow Sept. 6, 1949 Goddard June 6, 1950 Southworth Sept. 26, 1950 Mumford July 31, 1951 Fenn Aug. 28, 1951 FOREIGN PATENTS Great Britain Oct. 19, 1948 

